CONIDIUM PRODUCTION IN PENICILLIUM 1 
Charles Thom 
Certain morphological features are common to the species which 
for convenience are lumped together under the generic name, 
Penicillium. 
CONIDIOPHORES 
The fertile hyphae or conidiophores may arise as branches from 
submerged or from aerial hyphae. They are septate except when 
they are very short. They have approximately the same diameter 
as the vegetative hyphae from which they branch. They are uni- 
form in diameter from point of origin to the point where the 
conidium-producing complex of cells begins to form. The apex 
of the uppermost cell is frequently though not always swollen 
somewhat like the vesicle of Aspergillus, and the distal ends of 
branches if such are present are commonly also swollen, but the 
appearance of such swelling is not a uniform character within the 
species. The conidiophore proper should be measured from the 
point of origin to the base of the fruiting group of cells or 
branches. This part ceases to grow in length when fruiting com- 
mences, hence this measurement is more characteristic than a 
measurement including fruiting mass which frequently increases 
in length for several weeks by the production of new conidia. 
Conidial Apparatus 2 
The essential organ of conidium production in this group is 
the fertile cell which has been differently named by various work- 
ers as a basidium by Brefeld, Stoll, the writer in part, as sterigma, 
by Westling, Bainier, Wehmer, and others. The term “ conidii- 
ferous cell ” was used in the English descriptions of writer’s prev- 
ious paper because the word had no morphological significance in 
1 Published by permission of the Secretary of Agriculture. 
2 This section of the paper was presented to the Botanical Society of 
America at Washington, D. C., December 27, 19 11, under the title “The Con- 
nective between Conidia of Penicillium,” with an abstract appearing in Sci- 
ence, N. S., vol. 35, no. 891, January 26, 1912, pp. 149-150. 
211 
